The invention relates to the field of optical modulators, and in particular to external electro-optical (EO) modulators.
There are many different modulator technologies that are now in use. Various physical effects are used to modulate light beam: acousto-optic, electro-optic, electro-absorption, plasma density, thermo-optic, etc. High-speed optical communications are dominated by either direct modulation of the laser source or integrated/hybrid modulator. The most popular external modulators are based on electro-absorption (EA) in multi-quantum well materials or electro-optic effect in LiNbO3 (LN). EA modulators often require temperature control for proper operation and although they operate with low power, they have not proven cost-effective. LN modulators have excellent modulation specs, but are power-hungry and large.
There is no commercially available solution that allows seamless integration of large number of optical modulators to be used with electronics to tackle various tasks, from digital communications to analog optical signal processing. Much effort has been directed in recent years on plasma based silicon modulators that can be potentially integrated with electronics. The optical and electronic process requirements for fully integrated modulators are quite onerous and make it very difficult to adapt electronics and optics to ever-changing market needs and to take advantage of new process and material technologies.